Apparatus for making rolls

ABSTRACT

In the manufacture of metal cored elastomeric rolls having an outside protection sleeve, an extruded tubular sleeve of suitable material is placed in a mold having a cylindrical cavity of an inside diameter considerably in excess of the outside diameter of the sleeve, one end of the sleeve being anchored and the other end being free to move longitudinally. A cylindrical metal core is placed inside the sleeve and elastomeric material is then injected under pressure into the space between the core and the sleeve. The pressure stretches and expands the sleeve, forcing it into contact with the mold wall. The mold is then capped and heated to cure the elastomeric material.

. mute States Patent [191 1111 3,724,93 Nelson [451 Apr. 3, 1973 s41APPARATUS FOR MAKING ROLLS 3,355,772 12/1967 Kolberg ..18/29 x 3,613,16810/1971 Rowland et a1... ..l8/30 WC X [75] Invent William Sparta}3,015,855 1/l962 Markel ..264/127 [73] Assignee: Ames RubberCorporation, Hamburg, NJ. Primary Examiner-J. Howard Flint, Jr. Filed:Feb. 1971 Attorney-Sandoe, Hopgood & Callmafde [21] App1.No.: 116,883[57] ABSTRACT In the manufacture of metal cored elastomeric rolls [52]11.5. CI. ..425/129, 425/128, 425/468, having an outside protectionsleeve, an extruded tubu- 425/403, 425/242 lar sleeve of suitablematerial is placed in a mold hav- [51] Int. Cl. ..B29f 1/00 ing acylindrical cavity of an inside diameter con- [58] Field of Search..18/29, 36, 19 TM, 19 TC; siderably in excess of the outside diameterof the 249/83, 87, 97 sleeve, one end of the sleeve being anchored andthe other end being free to move longitudinally. A cylin- [56]References Cited drical metal core is placed inside the sleeve andelastomeric material is then injected under pressure UNITED STATESPATENTS into the space between the core and the sleeve. The 3,3 0,1204/1968 Rowland et a1 ..18/29 x pressure stretches and expands theSleeve, forcing it 2,684,502 7/1954 Paulve ...18/36X into contact withthe mold wall. The mold is then 3.402.753 1968 6 X capped and heated tocure the elastomeric material. 2,845,657 8/1958 Bearc ..249/83 X2,864,130 12/1958 Beare ..249/83 X 7 Claims, 4 Drawing Figures I I2 2 .1I 8 3 1 3 5 4 l5 ,3 2 H l I y 1 If I0 I a l I L. 1 h 1 5 11. If IAPPARATUS FOR MAKING ROLLS This invention relates to apparatus formaking metal cored elastomeric rolls having an outside tubularprotective sleeve.

Such rolls have a variety of uses in various types of apparatus. Oneimportant use is in electrostatic copying machines in which such rolls,sometimes referred to as fuser rolls are used to feed copy paper to andthrough the stage where the electrically charged particles are fused tothe paper at relatively high temperaturesand at relatively highpressures. For this particular use the performance requirements are veryhigh. The rolls must conform to close tolerances dimensionally, theymust be stable dimensionally, the elastomeric body must be heatresistant and of a predetermined hardness, and the protective sleevemust be not only heat and abrasion resistant, but also it must remainbonded securely to the elastomeric body during and after repeatedflexings over prolonged periods of use.

Heretofore it has been known to use solid polymers oftetrafluoroethylene obtainable commercially under the trademark or tradename TEFLON as the material from which the tubular protective sleeveshave been fabricated. Silicone rubber has commonly been used as theelastomeric material. According to a known method of making such rolls acylindrical body of elastomeric material is molded onto the metal coreand cured thereon. Thereafter a sleeve of heat shrinkable TEFLON of adiameter slightly larger than the prescribed final outside diameter ofthe elastomericbody is placed over the elastomeric body with adhesiveand is then subjected to heat. The heat applied causes the sleevematerial to shrink and thereby become securely bonded to the elastomericmaterial. One difficulty with this method is that it is difficult tomaintain dimensional tolerances in the finished rolls. Moreover, thebond between the sleeve and the elastomeric material tends to becomeloosened or cracked by repeated flexing.

According to the present invention tubular sleeves of such material areextruded to an outside diameter which lies between the outside diameterof the core and the inside diameter of the mold cavity. Such a tubularsleeve is placed inside the mold cavity, concentric with the core andthe mold cavity but spaced from both. One end of the sleeve is thenanchored securely at the inlet end of the mold while the other end isguided to maintain concentricity, but is free to move longitudinally.The inlet end of the mold, which is provided with one or more inletopenings through which the elastomeric material may be injected into themold, is then attached to a conventional extruder. The outlet end of themold is capped, but the cap is provided with an orifice of restrictedarea adapted to restricted egress of air as the elastomeric material isinjected.

Elastomeric material is then injected into themoldinto the space betweenthe core and the sleeve.

As the injection of elastomeric material continues, air is expelledthrough the orifice, and the elastomeric material eventually fills thespace between the core and the sleeve. At this time due to therestricted egress of material from the mold, a back pressure is built upwhich causes the sleeve to stretch and expand outwardly against the wallof the shell. The free end of the material through the orifice, the moldis removed from the extruder.

The inlet end is then capped. The orifice in the cap at the outlet endof the mold is preferably left open or partially open as a vent toprevent build up of excessive pressures within the mold during curing.The mold is then placed in a curing chamber and heat cured in accordancewith conventional practice.

A preferred embodiment of apparatus for carrying out the above describedmethod is shown in the accompanying drawings, in which:

FIG. 1 is a longitudinal section through the mold.

FIG. 2 is a section on the line 22 of FIG. 1.

FIG. 3 is a section on the line 33 of FIG. 1.

FIG. 4 is a side elevation of the finished roll, partly in section.

Referring to the drawings, the mold comprises a tubular outer shell 1having a smooth cylindrical bore 2 which forms the wall of the moldcavity, and having externally threaded ends 3 and 4. The end 3 is theinlet end of the mold through which elastomeric material is injectedinto the mold. This end is provided with a support member which includesmeans to grip and hold the end of a tubular sleeve S. In the embodimentillustrated the support member includes a plug 5, the centersurface ofone end of which is tapered as shown at 5', and a collar 6, so that asthe two parts of the support member are assembled with the end of thesleeve S located between the tapered surface of the plug and the insidesurface of the collar, it is gripped and held tightly against endwisemovement as elastomeric material is injected into the mold.

The end 4 is the discharge end. It is provided with a second supportmember comprising a plug 7 and collar 8. The exterior end of plug 7 fitssnugly into the collar 8 in sliding relation therewith, which, in turn,fits snugly into the outer shell. However, the interior end of the plugis of slightly reduced diameter so that when the plug is assembled withthe collar a cylindrical groove 9 is provided to receive and guide theend of the tubular sleeve S without restricting its endwise movement.

Each of the end plugs 5 and 7 is counterbored to provide shoulders 10,10' to support and center the metal core 1 l. The said core may beeither solid or tubular, as shown. Each of the end plugs is providedwith a plurality of ports l2, 12' of small diameter opening into thespace between the core and the sleeve. The ports 12 in the plug 5 serveas inlet ports through which the elastomeric material may be injectedinto'the mold in the space between the core 11 and the sleeve S. The

ports 12' in the plug 7 are preferably of smaller diameter and less innumber than those in the plug 5 and they serve as discharge portsthrough which air may be expelled as the mold is filled with elastomericmaterial. Each of the collars 6 and 8 is provided with a beveled surface13, 13' which extends to and meets the cylindrical bore 2 of the shellin order to provide beveled surfaces at each end of the roll.

An internally threaded end cap 14 is provided for the inlet end of themold and a similar internally threaded cap 15 is provided for the exitend of the mold. The cap 15 is provided with an orifice of restrictedarea 16 for the egress of air. The plug 7 is provided with an annulargroove 17 formed in its outer surface which provides communicationbetween each of the ports 12 and the orifice 16. The orifice may, ifdesired, be closed by a set screw 18 which may or may not be providedwith a small bleed passage 19 for reasons hereinafter explained.

In the use of the mold in the practice of the process, one end of thetubular sleeve S is inserted into the space between the opposed taperedsurfaces of the plug 5 and collar 6, and the two parts are pressedtogether until the end of the collar is flush with the end of the plugas shown in the drawing. This locks the end of the tubular sleeve firmlyin position.

Next, the metal core is placed inside the sleeve S and is seated on theshoulder provided by the counterbore of the plug 5. Then with thisassembly in upright position, the plug 7 is inserted in the sleeve andthe shoulder provided by the counterbore of the plug is seated on theend of the core. The collar 8 is then slid over the plug 7 and thesleeve. The assembly is then inserted into the mold shell. The end capis. now placed over the end of the shell and screwed down. Finally, theend 3 of the shell is screwed into an extruder. The assembly is nowready for the molding operation.

The extruder is now operated to force the elastomeric material throughthe ports 12 into the space between the central core and the sleeve S.As the injection of material continues, a back pressure begins to buildup in the mold which begins to stretch and expand the sleeve S outwardlytoward and against the wall of the shell and the beveled surfaces 13.Injection of the material is continued until air has been completelyexpelled from the mold and elastomeric material begins to be expelledthrough the orifice 16 in the cap 15. At this point the sleeve has beenstretched and expanded into firm contact with the wall of the shell andthe beveled surfaces 13 throughout the entire areas thereof. There is nocontact of the injected material with either ofthese surfaces.

During the injection of elastomeric material the set screw 18 is usuallyremoved, and air escapes through the orifice 16. However, if restrictionis required, a set screw having a bleed passage of the desired size maybe inserted.

After the mold is completely filled, the shell is unscrewed and removedfrom the extruder, and the cap 14 is attached and screwed down tightly.The mold is now ready to be placed in a heated curing chamber to curethe elastomeric material. In most cases it is desirable to leave open avent passage during curing such as is provided by the orifice 16 or by ableed passage 19 in the set screw 18, in order to provide for possibleexpansion of the elastomeric material. However, this depends oncircumstances, and particularly on the composition of the elastomericmaterial and its hardness. In some cases where the composition is verysoft, either no orifice is required or at most a very small bleedorifice is required. However, with harder compositions, a vent isusually required to prevent rupture of the mold.

In the manufacture of rolls for use as fuser rolls in electrostaticcopying machines, silicone rubber is preferably used as the elastomericmaterial and is compounded to a hardness level as specified by themanufacturers of the machines, as for example, in the range between l5and 40 Shore A. A typical outside diameter of such rolls might be 2.40inches and the length might be approximately 19 inches. The diameter ofthe metal core of such rolls might be 1.75 inches so that within themold there would be a space between the outside wall of the core and theinside wall of the mold shell of approximately 0.325 inches. Under thesecircumstances, the Teflon tubing would be extruded to an outsidediameter of approximately 2 inches and a wall thickness of 0.02 inches.During the injection of the elastomeric material, therefore, the tubingwould be stretched from a diameter of 2 inches to a diameter of 2.40inches. As stretching takes place, the end of the sleeve is permitted tomove longitudinally in the groove 9.

Such rolls would customarily be cured at a temperature of approximately340 F. for a period of 60 to minutes.

It will be understood that the invention may be variously modified andembodied within the scope of the subjoined claims.

I claim as my invention:

1. A mold for making metal cored elastomeric rolls having an outsidesleeve of material in tubular form, comprising an outside shell having acylindrical mold cavity therein, a support member at each end of themold cavity, one of said support members at the inlet end of said cavityhaving ports through which elastomeric material may be injected into themold cavity, and the other of said support members at the discharge endof the cavity having ports through which air may be discharged from themold cavity, said support members at the inlet end of said cavity havingmeans to support one end of a cylindrical sleeve of material spaced frombut in concentric relation to the wall of the mold cavity and to locksaid end of said cylindrical sleeve against longitudinal movement awayfrom said inlet end of said cavity, and the other of said supportmembers having means to support the other end of said sleeve inconcentric relation to the wall of the mold cavity and to hold said endof said sleeve against radial movement without restricting longitudinalmovement away from the discharge end of the cavity.

2. A mold according to claim 1 in which said first named support memberat the inlet end of said cavity comprises a plug and a collarsurrounding said plug, the surface of said plug being tapered, and inwhich the end of said sleeve at the inlet end of the cavity is lockedbetween the tapered surface of the plug and the collar.

3. A mold according to claim 1 including means for restricting thedischarge of material from the mold cavity comprising an end cap havingan orifice of restricted area therein.

4. A mold according to claim 2 in which said second named support memberat the discharge end of the cavity comprises a plug and a collarsurrounding said plug in sliding engagement therewith, one end of saidplug being of reduced diameter to provide a groove to receive andsupport the end of the sleeve at the discharge end of the cavity.

restricting the discharge of material from the mold l cavity comprisingan end cap at the discharge end of the cavity having an orifice ofrestricted area therein.

7. A mold according to claim 6 in which the ports in said second namedsupport member at the discharge end of the cavity extend through theplug thereof, said plug having an annular groove in its end face communicating with said ports and communicating with the orifice in said endcap.

2. A mold according to claim 1 in which said first named support member at the inlet end of said cavity comprises a plug and a collar surrounding said plug, the surface of said plug being tapered, and in which the end of said sleeve at the inlet end of the cavity is locked between the tapered surface of the plug and the collar.
 3. A mold according to claim 1 including means for restricting the discharge of material from the mold cavity comprising an end cap having an orifice of restricted area therein.
 4. A mold according to claim 2 in which said second named support member at the discharge end of the cavity comprises a plug and a collar surrounding said plug in sliding engagement therewith, one end of said plug being of reduced diameter to provide a groove to receive and support the end of the sleeve at the discharge end of the cavity.
 5. A mold according to claim 1 in which said second named support member at the discharge end of the cavity comprises a plug and a collar surrounding said plug in sliding engagement therewith, one end of said plug being of reduced diameter to provide a groove to receive and support the end of the sleeve at the discharge end of the cavity.
 6. A mold according to claim 5 including means for restricting the discharge of material from the mold cavity comprising an end cap at the discharge end of the cavity having an orifice of restricted area therein.
 7. A mold according to claim 6 in which the ports in said second named support member at the discharge end of the cavity extend through the plug thereof, said plug having an annular groove in its end face communicating with said ports and communicating with the orifice in said end cap. 